The global economic expansion has stressed the transportation industry's ability to keep up with the shipping demands for raw materials and finished products. Indeed, the demand for qualified tractor-trailer drivers has far outstripped the ability of the industry to recruit and train individuals to fill the demand of the marketplace. As a result, the demand of the transportation industry to utilize the existing personnel and vehicles has resulted in increased time spent on the road and in the vehicles in an attempt to meet the market demands.
In an effort to maintain the safety of the highways, federal regulations governing the amount of time that a driver may spend behind the wheel have been instituted. When such maximum times have been reached, the driver is required to take his vehicle off the road and rest. The number of trucks pulled over at toll plazas, weight stations, and rest stops illustrates the compliance with such regulations. However, these locations often do not provide anywhere for the drivers to rest, necessitating continued occupancy within the vehicle.
In response to the needs of the transportation industry and in recognition of the locations where drivers are forced to rest, over-the-road vehicle manufacturers have continued to increase the emphasis on ergonomic factors in the design and manufacturer of their vehicles. Indeed, the interior of a modem over-the-road vehicle contains many features to minimize the stress and fatigue placed on the drivers during the operation of the vehicle. These features include vibration dampers and lumbar supports in the seats, increased sound insulation, and heating, ventilation, and air conditioning (HVAC) systems that provide a comfortable environment for the driver. To accommodate the required rest periods, and in recognition of the increased usage of driving teams, which typically include two individuals, one who drives while the other sleeps, many over-the-road vehicles include a sleeping compartment. This sleeping compartment is also temperature controlled so that time spent therein provides the occupant with a restful experience.
Unfortunately, the current state-of-the-art heating and air conditioning systems utilize engine-belt driven compressors for the air conditioning system to circulate and pump the refrigerant throughout the vehicle to cool the passenger compartments. An engine-belt driven pump is also utilized to circulate the engine waste heat throughout the passenger compartments when heating is required. While such systems are ideally suited to provide a temperature controlled environment during operation of the vehicle, neither of such systems is able to operate when the engine is turned off.
As a result of the inability of the current state of the art of vehicle HVAC systems to operate while the vehicle's engine is turned off, the over-the-road vehicle operators are forced to choose between two less than ideal situations while trying to rest. First, they may choose to continuously run their vehicle's engine so that they may have heating or air conditioning while they rest. Alternatively, they may choose to turn off their engine and try to rest in a non-temperature controlled environment, although temperatures can often reach extremes of high and low depending on where the vehicle happens to be when a required rest period is reached. While the first option improves safety by providing a comfortable resting environment for the driver, it greatly increases the cost of operating the over-the-road vehicle as the engine is continued to run, which burns additional fuel, simply to operate the heating or air conditioning system. Similarly, while the second option does not increase the cost of operating the vehicle because the engine is turned off, the driver may not fully be able to rest in an environment of temperature extremes, thus potentially reducing the safety of the operation of the vehicle.
There exists, therefore, a need in the art for a vehicle heating, ventilation, and air conditioning (HVAC) system that is able to provide conditioning of the interior of the vehicle, not only during periods of engine operation, but also during engine off or no-idle conditions.